This study is designed to investigate the treatment efficacy of 8 weeks swallowing exercise programs for patients with NPC after radiation therapy. This study also compares two different swallowing exercise: effortful swallow and Mendelsohn's maneuver, to see which one can bring more benefits to patients after a certain period of exercise training. Three assessment tools are selected to evaluate the study result: Mann Assessment of Swallowing Ability (MASA), videofluoroscopic swallowing study (VFSS), and Chinese version Swallowing Quality-of-Life Questionnaire (CSWAL-QOL). The hypothesis of this study is that the effortful swallowing exercise would have better treatment efficacy.